Within the medical field, there is a need to determine the in vivo conditions of gas equilibrium within the blood of a patient. Medical personnel will typically be concerned with the partial pressures of oxygen, and carbon dioxide. They are also concerned with those ionic species whose activities are related to blood gas equilibria, such as, the activities of hydrogen and calcium ions.
For a blood sample to be valid for blood gas analysis, the sample must be collected under anaerobic conditions, i.e., collected so that the blood is not exposed to gases outside of the patient's body, to thereby avoid a shift in the partial pressures of the gases to be examined. Current and commercially available arterial blood sampling devices are not generally adequate for ensuring the integrity of anaerobic blood sampling. As an example of a prior art device, a syringe and a vented plunger is used to slowly withdraw blood from the patient into the barrel of the syringe by pulling the vented plunger away from a zero airspace within the barrel until the correct volume of blood is obtained from the patient. These devices, however, still allow for a certain degree of exposure of the blood sample to outside air. A certain amount of outside air will be contained within the barrel prior to any movement of the plunger. Accordingly, the initial portion of blood will be exposed to this air thereby altering the partial pressures of gases contained in this initial sample. Since no means are provided for discarding the initial portion of blood withdrawn, the entire sample will be contaminated.
Furthermore, using the above-described device, no provision is made for protecting the medical operator of the device against accidental puncture or exposure to contaminated blood during the procedure.
Other devices, such as the Becton and Dickenson (BD) Vacutainer and Vacutainer Adapter display improved performance in protecting the medical operator from exposure to withdrawn blood. These devices too, however, allow a certain amount of exposure of the initial portions of the blood sample to outside air, thereby contaminating the entire sample.
In addition to the foregoing inadequacies of the prior art, no blood sampling device is presently known which provides means for flushing or infusion of fluid, e.g., nutrients, drugs, etc., into the bloodstream while also allowing removal of an anaerobic blood sample.
Accordingly, it is desirable to provide apparatus for extracting an anaerobic blood sample from a patient. It is further desirable to provide apparatus for extracting a blood sample which also allows fluids to be infused into the bloodstream of the patient. It is further desirable to provide such a device which will allow for taking repeated samples without the need to make additional punctures or needle placements. It is also desirable to provide a device for extracting blood samples, which device may be left on the patient for scheduled interval sampling, or other subsequent sampling.